Conductive springs and ball acceleration switch



July 21, 1964 J. M. BOYLE ETAL CONDUCTIVE'SPRINGS AND BALL ACCELERATIONSWITCH Filed Oct. 1'7, 1962 INVENTORS. JOHN M. BOYLE EARL J. DONALDSONATTORNEY United States Patent 3,141,936 CONDUCTKVE SPRHNGS AND BALLACQCELERATEQN SWTTGZH John M. Boyle and Earl .l. Donaldson, (ChinaLatte, Calif., assignors to the United States of America as representedby the Secretary of the Navy Filed 0st. 17, 1962, Eser. No. 231,3tl

8 Claims. (Cl. 2tltl-61.53)

(Granted under Title 35, US. Code was sec. 2%)

The invention herein described may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

This invention relates to an acceleration responsive device, and moreparticularly to a switch which is activated to close an electricalcircuit when a desired value of acceleration is imparted, in apredetermined direction, to the switch.

Among the most critical problems confronting designers of accelerationresponsive switches has been the lack of sensitiveness and reliability,as well as excessive size and complexity, which is overcome by thepresent invention.

The general purpose of this invention is to provide a simple, sensitive,compact and inexpensive acceleration switch capable of operating in areliable fashion even though subjected to conditions of severevibration.

Therefore, an object of the present invention is to provide anacceleration switch which functions to close an electrical circuit whenan accelerating force of a desired value is imposed on the switch in agiven direction.

Another object is to provide an acceleration responsive device which isresponsive to linear acceleration of a predetermined value while beinginsensitive to incident shock and vibration.

Other objects, advantages and novel features of the invention willbecome apparent from the following detailed description of the inventionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view of an assembled switch device or" thepresent invention;

FIG. 2 is a larger scale axial cross sectional view, taken generallyalong lines 2-2 of PEG. 1, illustrating an open condition of the switch;

FIG. 3 is a fragmentary View similar to FIG. 2 but illustrating a closedcondition of the switch; and

FIG. 4 is a view similar to FIG. 3, but of a modification of the device.

Referring now to the drawings, wherein like reference numerals designatelike or corresponding parts throughout the several views, there is shownin FIG. 1 a switch, generally designated by reference numeral 1%, havinga ceramic tubular housing 11, a metallic sealing plug 12, an access port13 (FIG. 2), an access closure 13, and a pair of electrical leads 14 and14.

Turning now to FIG. 2, the metallic plug 12 is secured to the housing 11by suitable means, such as solder 12', which serves to secure the plug12 to a metalized insert portion 11 of the housing 11. Leads 14 and 14are connected to switch terminals 15 and 15, respectively, which serveto couple the switch 1th to a given circuit. The circuit forms no partof the present invention, but it is understood that closing of theswitch under predetermined conditions of acceleration causes the circuitto perform various desired functions, such as, for example, controllingignition of propellants of various stages of multi-stage rocket motorswhen the motor has had desired acceleration imparted thereto. Theterminal 15' is mounted on a disk-like member, generally designated byreference 16, having an electrical contact surface 16'. The disk 16 withits surface 16' is secured by solder 12", or other suitable means, to anadjacent metalized insert portion 11" of the housing 11. Acompression-type coil spring 17, calibrated for reasons as willhereinafter become apparent, is seated with one end engaging the surface16 so as to provide an electrical contact therebetween and to permit acir cuit to be established between the terminal 15' and a spherical mass18 which is seated in electrical contact with the opposite end of thespring 17 in such a manner as to be biased toward plug 12. and away fromsaid disk member 1%, for effecting a normally open condition between theterminals of the switch, and in a manner which allows the mass 18 to bestabilized in the normally open condi tion through contact with the plug12.

The lead 14 is connected through terminal 15 to one end of a centercontact pin or post 19. The opposite end of post 19 extends inwardlyinto housing 11, within the supported coil 17, through a hermeticallysealed, insulator portion 16" of the disk 16, FIG. 2. Surrounding theinwardly extending end portion of pin or post 19, and in electricalconducting engagement therewith, is a resilient electrical contact inthe form of a coil spring 21 having one end seated on the portion 16 ofthe disk 15 in such a manner as to be electrically insulated from thesurface 16'. The spring 21 extends a short distance beyond the inwardlyextending pin 19, as shown in FIG. 2, while being of a lengthinsufficient to contact the mass 18, to thus establish an air gapbetween the end of the spring 21 and the mass 18, and consequently tothus establish an open circuit. Therefore, it is understood that tobridge the air gap, for completing the circuit between the terminals 15and 15', the mass 18 is moved axially of the housing 11 to deflect thespring 17 so that the mass 18 may contact the spring 21 to complete theelectrical circuit. In order to provide a Series of low electricalresistance contacts for the elements disposed between the terminals 15and 15, it has been found desirable to provide gold plating for thesprings 17 and 21, the spherical mass 18, the pin 19, and the surface16. This plating, or gold surfacing technique, provides for a circuit ofrelatively very low resistance, and accordingly relatively low voltagesources may be utilized for affording the numerous advantages normallyattending low voltage requirements.

As the switch of the present invention is intended to close anelectrical circuit when an accelerating force of a desired value isimposed on the device in a direction such that inertia of mass 1% causesthe spring 17 to deflect, it is necessary that both of the springs 17and 21 be calibrated. The calibration of spring 17 is effected throughobserving the deflection of the spring acting under a force equal to themass of the sphere times the acceleration required to close the switch.The value of the spring 17 may be just slightly less than the valuerequired to maintain an open circuit so that contact chatter" may beobviated at the instant the desired value of acceleration is imposed forclosing the switch. When an acceleration value greater than the desiredvalue is imposed on the device, the spherical mass 13 deflects springs17 and 21 and comes to rest, or seats on the pin 19, FIG. 3, and remainsso seated until acceleration diminishes to a value which allows springs17 and 21 to unseat the mass. The spring 21, however, offers littleresistance to the mass 18 and accordingly is calibrated primarily as tolength so as to provide an air gap of a dimension dictated by theobserved deflection of spring 17. It is understood that the purpose ofthe spring 21 is to provide a resilient contact which engages the mass13 to complete a circuit in a manner which tends to obviate contactchatter through allowing the mass 13 to be engaged in a floatingfashion.

An insulating damping fluid 22, which may be a gas or a liquid, such asa well known silicone fluid, is introduced through the port 13 toprovide a damping of undesired movements of the mass 18, which may occurin operation as a result of incident vibrations being imposed thereon.Since the relative dimensions of the cylinder and of the spherical mass13 may be varied as necessary, fluid passage around the mass may bevaried as desired.

Referring now to FIG. 4, a modification of the above described deviceutilizes a metallic cylinder or housing 25, which may be gold plated forthe purposes hereinabove described, and is provided with a lead 26connected therewith and extending directly to ground in such a mannerthat the spring 17, which is in normal electrical contact with thecylinder 25, the cylinder 25, and the spherical mass 18' are constantlygrounded by the given structure to which the device is operativelyattached. Therefore, when an acceleration of desired value is attained,the grounded mass 18' engages the spring 21 in the manner hereinabovedescribed, and a circuit between the lead 14 and ground lead 26 iscompleted through the switch.

The device shown in FIG. 4 has been found particularly satisfactorywhere the device is to be continually re-used, as the metallic walls ofthe cylinder 25 tend to be less abrasive than the less expensive ceramiccylinder of housing 11, while the ceramic housing material is usedprimarily for one shot operations wherein the device is destroyed.

The operation of the device of the present invention may best beunderstood with reference being made particularly to FIGS. 2 and 3. Thehousing Eli is mounted in a manner such that the switch actuatingacceleration force is applied in an axial direction extending from thespring 21 to the mass 18. When the force attains a pre-selected value,the pre-calibrated spring 117 deflects under the influence of the mass18 to the extent necessary for displacing the mass 18, from a stabilizedcondition adjacent the plug 12, into electrical contact with the spring21 to close the switch between leads of the circuit to which the switch10 is coupled. It is noted that the leads 14 and 1 4, FIG. 3 connect theswitch 10 between components of an electrical circuit, while, as shownin FIG. 4, the lead 26 extends from the switch housing 25 directly toground to establish a circuit between lead 14 and ground. Therefore, itis understood that the mass 18', FIG. 4, may contact the cylinder 25, aswell as the spring 17, since the mass 18' is to be continuouslyconnected to ground.

Thus, there has been provided a compact acceleration switch capable offunctioning in a reliable manner even though subjected to severevibration. This function is attained through utilizing a pair ofresilient electrical contacts and a metallic mass supported on one ofthe contacts which serves to deflect for bringing the mass into contactwith the other contact of said pair in order that the circuit be closedwhen acceleration is imposed on the switch in a predetermined direction,thereby providing a chatter-free closed switch.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. An acceleration responsive switch comprising in combination:

an elongated tubular switch housing having a first and a second end;

a substantially flat, di-electric disk member disposed within the firstend of said housing in a plane trans verse to the longitudinal axis ofsaid housing and having an opening near the center thereof;

a first electrical conductor having a ring-shaped configuration fixed tosaid disk member and being disposed within said housing and arranged inco-axial alignment with respect to said opening and radially displacedtherefrom;

means fixedly securing said disk member within said first end of saidhousing;

a second electrical conductor comprising an elongated electrical currentconducting post fixed to said disk and disposed to extend in an axialdirection through said opening and to terminate at a terminal pointlocated within said housing near the first end thereof and between saidfirst conductor and the second end of said housing;

a third electrical conductor comprising a first elongated coil springsupported at its first end by said first conductor being so disposed asto be co-axially aligned and radially displaced with respect to saidsecond conductor and having its second end disposed in a transverseplane located between the second end of said tubular housing and saidterminal point;

a fourth electrical conductor comprising a second elongated coil springbeing engaged and supported near its first end by said second electricalconductor in coaxial alignment therewith and in a radially displacedrelationship with respect to said third electrical conductor, and beingso arranged as to have its second end disposed in a transverse planelocated between the second end of said third conductor and said terminalpoint; fifth conductor comprising a movable solid mass seated on andsupported by said second end of said first coil spring in a displacedrelationship with respect to said second end of said second coil springto thus establish a switch-open air gap between said mass and secondcoil spring; and a damping fluid disposed to surround said conductors,whereby the inertial forces of said mass and given forces ofacceleration acting in a predetermined direction may effect a gradualdeflection of said first coil spring for thus permitting said mass toseat on the second end of said second coil spring, and, subsequently todeflect said second coil spring for thus permitting said mass to seat inengagement with said second electrical conductor to thus establish anoperative closed condition for said switch.

An acceleration switch including:

a pair of radially displaced concentrically arranged electricalcontacts;

a pair of elongated, concentrically aligned and radially displaced coilspring conductors, each being separately supported at a first endthereof by a given contact of said pair of contacts;

a displaceable solid mass of electrical conducting material seated onthe second end of one of said springs and biased thereby to assume adisplaced relationship with respect to the second end of the otherspring of said pair of coil springs to thus establish an airgap betweenthe mass and the other spring; and

an electrical circuit lead connected with each contact of said pair ofcontacts, whereby an electrical circuit may be completed between saidleads by causing said mass to act against and compress said one of saidsprings sufliciently for eliminating said air-gap.

3. A device as defined in claim 2, further including: a housingcomprising a sealed cylinder for mounting said switch; and damping fluiddisposed within said cylinder so that movement of said mass in saidcylinder may be damped against incident vibration.

4. The device as defined by claim 3, further characterized in that thesealed cylinder is formed of ceramic material having metalized sealingportions at each end thereof.

5. The device as defined by claim 3, further characterized in that thecylinder is formed of an electrical conducting metal with one of theleads of said pair being connected to one of said contacts by beingconnected to said cylinder.

6. The device of claim 5, wherein each of the electrical contactsurfaces comprises a gold plated surface.

7. An electrical switch comprising:

support means;

a first electrical contact comprising a first elongated coil springmounted on said support means;

a second electrical contact comprising a second elongated coil springmounted on said support means and being generally concentricallydisposed and radially displaced with respect to said first contact;

a movable mass of electrically conductive material supported by one endof said first contact and being normally spring-biased in an axialdirection away from second elongated coil spring by said first elongatedcoil spring to assume an axially displaced disposition with respect tothe second coil spring to provide an air-gap between the mass and thesecond coil spring to thus establish a switch-open condition for saidswitch when said switch is at rest; and

circuit leads connected with said first and said second contacts,whereby the air-gap may function to provide an open-circuit between saidleads, and which may be closed by imposing a state of acceleration onsaid switch for initiating a compression of said first coil spring forseating the mass on said second spring to eliminate said air-gap.

8. In an acceleration switch of the type adapted to provide anopen-circuit between switch-connected leads when a state of equilibriumis imposed on the switch and to provide a closed-circuit between theleads when a predetermined state of acceleration is imposed on theswitch, means comprising:

a di-electric base member;

a first conductor comprising a post having one end portion fixed to saidbase and its other end extending normally therefrom;

a second conductor comprising a compressible coil spring seated on thebase and coiled about said post in engagement therewith, being adaptedto have one end thereof extended beyond the extended end of the postunder the influence of spring recovery forces possessed by said spring,and adapted to retract under the influence of externally appliedcompression forces directed in a compressing direction against theextended end thereof;

a third conductor comprising a second compressible coil spring seated atone end on said base and extending normally from said base in asurrounding and radially spaced relationship with respect to said firstcoil spring and adapted to extend the other end thereof beyond theextended end of said first coil spring and adapted to be compressed bycompression forces acting against the extended end of the spring in aspring compressing direction;

a fourth conductor comprising a solid mass seated on and operativelysupported by the extended end of the second coil spring and being biasedto a displaced disposition with respect to the extended end of the firstcoil spring and the post by the recovery forces possessed by the secondcoil spring when a state of equilibrium is imposed on said switch, andseated in contact with the post when predetermined forces ofacceleration are imparted to the switch for causing the first and secondcoil springs to be compressed against said mass;

means maintaining the mass in its seated position on said second coilspring; and

a circuit lead connected with said first and said third conductors,whereby an open-circuit may be established between said fourth and saidsecond conductor when a state of equilibrium is imposed on said switch,and a closed-circuit may be established as predetermined acceleration isimposed on said switch for causing said fourth conductor to seat on saidfirst conductor.

Smith July 12, 1949 Waldow May 20, 1958

2. AN ACCELERATION SWITCH INCLUDING: A PAIR OF RADIALLY DISPLACEDCONCENTRICALLY ARRANGED ELECTRICAL CONTACTS; A PAIR OF ELONGATED,CONCENTRICALLY ALIGNED AND RADIALLY DISPLACED COIL SPRING CONDUCTORS,EACH BEING SEPARATELY SUPPORTED AT A FIRST END THEREOF BY A GIVENCONTACT OF SAID PAIR OF CONTACTS; A DISPLACEABLE SOLID MASS OFELECTRICAL CONDUCTING MATERIAL SEATED ON THE SECOND END OF ONE OF SAIDSPRINGS AND BIASED THEREBY TO ASSUME A DISPLACED RELATIONSHIP WITHRESPECT TO THE SECOND END OF THE OTHER SPRING OF SAID PAIR OF COILSPRINGS TO THUS ESTABLISH AN AIRGAP BETWEEN THE MASS AND THE OTHERSPRING; AND AN ELECTRICAL CIRCUIT LEAD CONNECTED WITH EACH CONTACT OFSAID PAIR OF CONTACTS, WHEREBY AN ELECTRICAL CIRCUIT MAY BE COMPLETEDBETWEEN SAID LEADS BY CAUSING SAID MASS TO ACT AGAINST AND COMPRESS SAIDONE OF SAID SPRINGS SUFFICIENTLY FOR ELIMINATING SAID AIR-GAP